The invention relates to a conduit for transporting finely-divided or fine-granular, dry bulk materials having a material conveyance zone and a zone for introducing the fluidizing medium separated from the first mentioned zone by a material which is permeable to gas and fluids. Further, the invention also relates to a process for operation of the said conduit.
Special bulk material conveyance means have been in existance for a long time and have been successfully employed in industry i.e. conveyance means which convert finely-divided and fine-granular, dry bulk materials into a fluid-like state with the aid of fluidizing gases. This causes the friction between the particles to fall to a very low value so that the bulk material behaves similar to a fluid.
If air, for example, is introduced through a porous base into bulk material resting on that base, and the device is in the form of a trough and is inclined downwards at a small angle of about 1.degree. to 6.degree. to the horizontal, then the bulk material will flow under the action of the force of gravity. Such conveyance means are known in industry as pneumatic conveyance conduits, airslides or fluidizing troughs.
The basic requirements for conduit transportation are the ability to fluidize the bulk material and the presence of a geodetic drop in elevation. If both of these conditions are met then conduit transport is, compared with other means of transport, very economical.
The principle of the fluidizing conduit is described for example in the manuals "Fordertechnik" 1967, VEB Publishers Technik, Berlin, on pages 280 and 281, and in Techniker-Handbuch, 1979 edition, published by Friedrich Vieweg and Son, Braunschweig/Wiesbaden.
Fluidizing conduits are employed for example in the cement, aluminum, chemical and foodstuffs industries. Significant advantages over mechanical means of conveyance are the simple construction, low energy consumption and thus better economics.
Depending on the nature of the bulk material, conveyance capacity and distance to be transported, a conduit with drop of up to 10% consumes between 0.04 and 0.075 kWh/t for transportation over a distance of 100 m. By comparison, the energy consumption for low density transportation over 100 mm is 1.5 to 3 kWh/t, likewise for a drop of 10%.
All known conduits of this kind, however, suffer a significant disadvantage in that transportation is possible only when there is a continuous drop in height. This places limits on the distance over which the bulk material can be transported using this means.
The object of the present invention is therefore to overcome this disadvantage and to develop a device which permits the use of a horizontal or even slightly upwards sloping conduit without having to sacrifice the economic advantages.